Size-dependent stability of supported gold nanostructures onto ceria : an HRTEM study
Résumé
Gold nanoparticles of various sizes, supported onto ceria, were synthesized using both deposition−precipitation and coprecipitation methods. Whatever the size, the study of the Au/CeO2 interface confirms the existence of two preferential orientation relationships with a dislocation network which compensates the 25% interfacial lattice mismatch. Behaviors of supported gold nanostructures under the electron beam were examined by high-resolution transmission electron microscopy (HRTEM). The thermal stability of the gold nanostructures was found to be strongly affected by the particle size. For small nanostructures (<5 nm), reversible shrinkage of gold layer by layer onto ceria surface was observed. For larger ones, a progressive and irreversible encapsulation by a CeO2−x layer was found and a four-step process was experimentally underlined.